Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may be used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle.
The controller typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition. A typical security system also includes a receiver associated with the controller. The receiver cooperates with one or more remote transmitters typically carried by the user and which are used to arm and disarm the vehicle security system, for example. Other remote control features, such as locking or unlocking vehicle doors may also be performed.
The alarm indication provided at the vehicle is important to the overall effectiveness of the security system. For example, a weak alarm indication may do little to deter a would-be thief. A thief may also be more likely to target a vehicle when the vehicle is among hundreds of vehicles in a large parking lot, for example. In such a situation, the thief may be comforted in knowing that the alarm indication will not be identified by the vehicle's owner, since many audible alarm indications are generic.
Another disadvantage with many conventional security systems, especially minimal feature systems as typically installed by vehicle manufacturers, is that no shock sensing capability is provided. Accordingly, the alarm will only sound for opening of the vehicle doors, for example, and not when the vehicle is towed or lifted onto a truck and carried away. Since there is no shock sensor typically on such minimal feature security systems, there is no ability to provide a prewarn alarm that is less than the full alarm. The prewarn alarm in feature-rich aftermarket security systems may desirably warn off a would-be thief before serious damage is done to the vehicle. The prewarn, if falsely triggered, is also less intrusive than a full alarm.